Add UseCounter for autocapitalize.

Source/core/html/HTMLTextAreaElement.idl

 /*
  * Copyright (C) 2006, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  * Copyright (C) 2011 Motorola Mobility, Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 55 matching lines @@
                                         unsigned long end,
                                         optional DOMString selectionMode = null);
     // TODO(philipj): The start and end arguments should be unsigned long and
     // should not be optional.
     void setSelectionRange([Default=Undefined] optional long start,
                            [Default=Undefined] optional long end,
                            optional DOMString direction);
 
     // HTML autocapitalize proposal
     // https://github.com/mounirlamouri/html-autocapitalize/blob/master/proposal.md
-    attribute DOMString autocapitalize;
+    [Measure] attribute DOMString autocapitalize;
 };